. The integration of sensory information from different parts of the visual field is a vital process underlying visual pattern recognition. The neuronal mechanisms mediating these integrative processes, however, are poorly understood. Evidence from theoretical, psychophysical and physiological studies suggest that specific, temporally coordinated interactions between spatially separate neuronal populations, within and between different areas of the visual cortex, mediate the integrative processes underlying visual perception. Extensive preliminary evidence, obtained from electrophysiological experiments in the cat, suggests that the stimulus-specific synchronization of oscillary neuronal responses within and between the cortical areas may provide a plausible mechanism for visual feature integration. The long-term objective of the proposed research is to perform a rigorous test of this hypothesis. Specifically, four sets of neurophysiological experiments are proposed to achieve this goal: 1) Record from pairs of closely spaced neurons within a cortical column in area 17 in the cat to determine the mechanisms underlying the generation and coordination of oscillatory neuronal responses. 2) Record oscillatory responses from spatially separate groups of neurons within area 17 of the cat, using multi-electrode techniques, to determine the conditions of visual stimulation which enable their temporal synchronization. 3) Record oscillatory responses from spatially separate groups of neurons in area 17 and a second area, 18 or PMLS, in the cat, to determine the conditions of visual stimulation which enable their temporal synchronization. 4) Record neuronal responses from areas V1 and V2 of the Macaque monkey, using single-unit as well as multi-electrode recording techniques, to determine if neurons within these areas exhibit stimulus-specific oscillatory responses, and if so, to determine what the cell type are, what their laminar positions within the cortex are, and the stimulus conditions under which they become synchronized. The results of these studies will enable future experiments to determine whether the interactions between oscillatory responses are utilized by a behaving animal to make perceptual discriminations.